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7  structures 529  species 0  interactions 1235  sequences 14  architectures

Family: TF_Zn_Ribbon (PF08271)

Summary: TFIIB zinc-binding

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TFIIB zinc-binding Provide feedback

The transcription factor TFIIB contains a zinc-binding motif near the N-terminus. This domain is involved in the interaction with RNA pol II and TFIIF and plays a crucial role in selecting the transcription initiation site. The domain adopts a zinc ribbon like structure [1].

Literature references

  1. Chen HT, Legault P, Glushka J, Omichinski JG, Scott RA; , Protein Sci 2000;9:1743-1752.: Structure of a (Cys3His) zinc ribbon, a ubiquitous motif in archaeal and eucaryal transcription. PUBMED:11045620 EPMC:11045620


External database links

This tab holds annotation information from the InterPro database.

InterPro entry IPR013137

Zinc finger (Znf) domains are relatively small protein motifs which contain multiple finger-like protrusions that make tandem contacts with their target molecule. Some of these domains bind zinc, but many do not; instead binding other metals such as iron, or no metal at all. For example, some family members form salt bridges to stabilise the finger-like folds. They were first identified as a DNA-binding motif in transcription factor TFIIIA from Xenopus laevis (African clawed frog), however they are now recognised to bind DNA, RNA, protein and/or lipid substrates [PUBMED:10529348, PUBMED:15963892, PUBMED:15718139, PUBMED:17210253, PUBMED:12665246]. Their binding properties depend on the amino acid sequence of the finger domains and of the linker between fingers, as well as on the higher-order structures and the number of fingers. Znf domains are often found in clusters, where fingers can have different binding specificities. There are many superfamilies of Znf motifs, varying in both sequence and structure. They display considerable versatility in binding modes, even between members of the same class (e.g. some bind DNA, others protein), suggesting that Znf motifs are stable scaffolds that have evolved specialised functions. For example, Znf-containing proteins function in gene transcription, translation, mRNA trafficking, cytoskeleton organisation, epithelial development, cell adhesion, protein folding, chromatin remodelling and zinc sensing, to name but a few [PUBMED:11179890]. Zinc-binding motifs are stable structures, and they rarely undergo conformational changes upon binding their target.

This entry represents a zinc finger motif found in transcription factor IIB (TFIIB). In eukaryotes the initiation of transcription of protein encoding genes by the polymerase II complexe (Pol II) is modulated by general and specific transcription factors. The general transcription factors operate through common promoters elements (such as the TATA box). At least seven different proteins associate to form the general transcription factors: TFIIA, -IIB, -IID, -IIE, -IIF, -IIG, and -IIH [PUBMED:1633439].

TFIIB and TFIID are responsible for promoter recognition and interaction with pol II; together with Pol II, they form a minimal initiation complex capable of transcription under certain conditions. The TATA box of a Pol II promoter is bound in the initiation complex by the TBP subunit of TFIID, which bends the DNA around the C-terminal domain of TFIIB whereas the N-terminal zinc finger of TFIIB interacts with Pol II [PUBMED:8516312, PUBMED:8504927].

The TFIIB zinc finger adopts a zinc ribbon fold characterised by two beta-hairpins forming two structurally similar zinc-binding sub-sites [PUBMED:8564536]. The zinc finger contacts the rbp1 subunit of Pol II through its dock domain, a conserved region of about 70 amino acids located close to the polymerase active site [PUBMED:15024075]. In the Pol II complex this surface is located near the RNA exit groove. Interestingly this sequence is best conserved in the three polymerases that utilise a TFIIB-like general transcription factor (Pol II, Pol III, and archaeal RNA polymerase) but not in Pol I [PUBMED:15024075].

More information about these proteins can be found at Protein of the Month: Zinc Fingers [PUBMED:].

Gene Ontology

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Domain organisation

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Alignments

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We make a range of alignments for each Pfam-A family. You can see a description of each above. You can view these alignments in various ways but please note that some types of alignment are never generated while others may not be available for all families, most commonly because the alignments are too large to handle.

  Seed
(71)
Full
(1235)
Representative proteomes NCBI
(1178)
Meta
(225)
RP15
(230)
RP35
(423)
RP55
(611)
RP75
(745)
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Format an alignment

  Seed
(71)
Full
(1235)
Representative proteomes NCBI
(1178)
Meta
(225)
RP15
(230)
RP35
(423)
RP55
(611)
RP75
(745)
Alignment:
Format:
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Sequence:
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We make all of our alignments available in Stockholm format. You can download them here as raw, plain text files or as gzip-compressed files.

  Seed
(71)
Full
(1235)
Representative proteomes NCBI
(1178)
Meta
(225)
RP15
(230)
RP35
(423)
RP55
(611)
RP75
(745)
Raw Stockholm Download   Download   Download   Download   Download   Download   Download   Download  
Gzipped Download   Download   Download   Download   Download   Download   Download   Download  

You can also download a FASTA format file containing the full-length sequences for all sequences in the full alignment.

External links

MyHits provides a collection of tools to handle multiple sequence alignments. For example, one can refine a seed alignment (sequence addition or removal, re-alignment or manual edition) and then search databases for remote homologs using HMMER3.

HMM logo

HMM logos is one way of visualising profile HMMs. Logos provide a quick overview of the properties of an HMM in a graphical form. You can see a more detailed description of HMM logos and find out how you can interpret them here. More...

Trees

This page displays the phylogenetic tree for this family's seed alignment. We use FastTree to calculate neighbour join trees with a local bootstrap based on 100 resamples (shown next to the tree nodes). FastTree calculates approximately-maximum-likelihood phylogenetic trees from our seed alignment.

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Curation and family details

This section shows the detailed information about the Pfam family. You can see the definitions of many of the terms in this section in the glossary and a fuller explanation of the scoring system that we use in the scores section of the help pages.

Curation View help on the curation process

Seed source: Pfam-B_1298 (release 17.0)
Previous IDs: TFIIB_Zn_Ribbon;
Type: Domain
Author: Finn RD
Number in seed: 71
Number in full: 1235
Average length of the domain: 42.80 aa
Average identity of full alignment: 34 %
Average coverage of the sequence by the domain: 11.75 %

HMM information View help on HMM parameters

HMM build commands:
build method: hmmbuild -o /dev/null HMM SEED
search method: hmmsearch -Z 23193494 -E 1000 --cpu 4 HMM pfamseq
Model details:
Parameter Sequence Domain
Gathering cut-off 25.8 25.8
Trusted cut-off 25.8 25.8
Noise cut-off 25.7 25.7
Model length: 43
Family (HMM) version: 7
Download: download the raw HMM for this family

Species distribution

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Structures

For those sequences which have a structure in the Protein DataBank, we use the mapping between UniProt, PDB and Pfam coordinate systems from the PDBe group, to allow us to map Pfam domains onto UniProt sequences and three-dimensional protein structures. The table below shows the structures on which the TF_Zn_Ribbon domain has been found. There are 7 instances of this domain found in the PDB. Note that there may be multiple copies of the domain in a single PDB structure, since many structures contain multiple copies of the same protein seqence.

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